In recent years, a fine processing technology for transferring a fine structure provided on a mold onto a member to be processed, such as a resin material, a metallic material, or the like, has been developed and has received attention. This technology is called nanoimprint or nanoembossing, and provides a processing resolving power on the order of several nanometers. For this reason, this technology is expected to be applied to a next-generation semiconductor manufacturing technology in place of a light exposure device, such as a stepper, a scanner, or the like. Further, the technology is capable of effecting simultaneous processing of a three-dimensional structure at a wafer level. For this reason, the technology is expected to be applied to a wide variety of fields as manufacturing technologies, and the like, for optical devices, such as photonic crystals, and the like, biochips, such as μ-TAS (micro total analysis system), etc.
When processing using such imprint is applied to the semiconductor manufacturing technology, e.g., as described in Appl. Phys. Lett., Vol. 67, Issue 21, pages 3114-3316 (1995) by Stephan Y. Chou et al., the processing is performed in the following manner.
That is, with respect to a work (workpiece), including a substrate (e.g., a semiconductor wafer), as a member to be processed, and a photocurable resin material disposed on the member to be processed, a mold provided with a desired imprint pattern is abutted and pressed against the photocurable resin material, followed by ultraviolet irradiation to cure the photocurable resin material. As a result, the imprint pattern is transferred onto the resin material layer. With the resin material layer as a mask layer, etching, or the like, is performed, to form a pattern on the substrate.
With respect to a mold used for such imprint, it is known that a coating layer is formed, on a surface of a mold body, of a material different from a material of the mold body, in some cases.
U.S. Pat. No. 6,916,511, shows, in FIG. 9, a coating layer 902 formed of silicon carbide, silicon nitride, or the like, on a surface of a mold body 90, to constitute a mold.
This coating layer functions as a protective layer for ensuring the strength of the mold surface.
However, the mold having the coating layer formed for ensuring the strength of the mold surface has been accompanied with such a problem that flatness is lost due to stress exerted at an interface between the mold and the coating layer. More specifically, as shown in FIG. 10, due to different materials for the mold body 901 and the coating layer 902, stress acts on the interface between the mold body 901 and the coating layer 902, to cause a phenomenon such that the mold is bent and deformed in some cases. As a result, the flatness of the mold is lost and, therefore, in-plane uniformity of imprint cannot be obtained.
In order to solve the problem of loss of the flatness, when the coating layer is formed at the entire rear surface of the mold, flatness is retained, but the following problems have arisen during alignment, through optical observation.
For example, even when a transparent material capable of transmitting therethrough optically observable light in a specific wavelength range is used, in a case when an opaque material incapable of optical observation is used for the coating layer, observation of an alignment mark is hindered. Further, even in a case when an optically observable transparent material is used for both the mold and the coating layer, light for optical observation can be reflected at the interface between the mold and the coating layer formed at the rear surface of the mold. In this case, when a thickness of the coating layer is close to a coherence length of observation light, unnecessary interference is caused to occur, thus hindering optical observation, in some cases.